The aim of this essay was to explore the causes of the obesity epidemic in the UK. The prevalence of obesity among children and adults has reached epidemic proportions over the past two decades and is a major public health concern in the UK. The causes of the obesity epidemic are complex and include environmental, behavioral and physiological factors. These factors influence the balance of energy intake and expenditure. It is crucial for the scientific and policy-making government as well as the public to understand the multidimensional factors, which influence obesity in order to implement the actions needed to reverse the epidemic.
Obesity has been defined by the World Health Organization (WHO, 2012) as “abnormal or excessive fat accumulation that may impair health”. The most frequently used measure of obesity and health is based on the body mass index (BMI), which is a single number that evaluates an individual’s weight in relation to height. Adults with a BMI of >30 kg/m2 are considered obese and those with a BMI equal to or more than 25 kg/m2 are overweight. Obesity increases the risk of a number of chronic illnesses, including cardiovascular disease, diabetes, hypertension and cancers (Kopelman, 2007) and therefore is a major public health concern.
2. Overview of the obesity epidemic
In the UK, the prevalence of obesity has more than doubled in the past 20 years (OECD Health Data, 2011). The latest Health Survey for England (HSE, 2010) figures show that 37.3% of adults (aged 16 or over) are overweight and a further 24.5% obese. The prevalence of obesity in children aged 2-10 is similarly alarming by increasing from 10.1% in 1995 to 14.6% in 2010. Recently reported modelling indicates that by 2025 some 40% of the British population could be obese (Foresight, 2007).
Because the physiological and psychological consequences of obesity can lead to increased morbidity and mortality, researcher, clinicians and government policymakers have explored a number of different causes that may explain the obesity epidemic. Understanding the causes of obesity has important implications for the actions that are needed to tackle and reverse the epidemic.
3. Causes of the obesity epidemic
In simple terms, the cause of obesity is an imbalance of energy intake and energy expenditure for a period of time, leading to an accumulation of excessive body fat. This energy imbalance is determined by the complex interactions of biology and behavior, set within a cultural, environmental and social framework. An obesity system map (Figure 1) was constructed by Vandenbroeck et al. in 2007 from data from several different research disciplines to represent the most comprehensive view of the determinants of energy balance.
Figure 1: A simplified version of the obesity system map (Source: Foresight systems map, 2007)
Although the causes for the obesity epidemic are complex and multifaceted, research evidence has identified changes in two main areas of our lifestyles that have driven the obesity epidemic. The first is the level of physical activity in the population (energy expenditure). People are spending more time indoors in front of the computer and TVs and less time outside running around. The second is the quantity and different food types we consume (energy intake). People consume more energy-dense food and eat fewer healthy foods. Both areas of this complex system are greatly influenced by psychosocial factors and the environment in which we live and work.
3.1. Energy expenditure
Research has shown that physical activity undertaken in the workplace and in the home has declined significantly in the UK over the past 30 years (Foresight, 2007). For example, in England, the average distance walked and cycled per person per year for transport purposes fell nearly by half in the time period from 1975 to 2003 (Foresight, 2007). The proportion of the population in an occupation requiring substantial physical effort has also reduced (Lobstein and Jackson, 2007). In addition, we are increasingly becoming reliant on work saving devices from washing machines to cars. For example, car use has risen steadily over the past 30 years, which was accompanied by changes in land use patterns to accommodate increased car use (Davis, 2007). Sheldon H Jacobson, a researcher who specializes in statistics and data analysis states in 2011 that the surge in passenger vehicle usage in the US between the 1950 and today correlates with surging levels of obesity. Data from the UK may find a similar association.
In the home, physical activity has been displaced by the availability and attractiveness of more sedentary activities such as television and computer games (Pereira, 2005; Biddle, 2010). Evidence suggests that television viewing is a major contributor to the obesity epidemic (Hancox et al., 2004; Viner, 2005; Rey-Lopez et al., 2011). This contribution arises from a combination of sedentary behavior, unhealthy mindless eating habits (Temple et al., 2007) and exposure to TV advertising for palatable, highly processed, energy dense foods (Cairns, 2008; Boyland et al., 2011).
Over extended periods, this decrease in physical activity can make a substantial difference to the energy balance (positive energy balance), which results in weight gain.
3.2. Energy intake
The hypothesis that people are eating more in their daily life is problematic to measure outside the laboratory and is greatly confounded by under-reporting by obese subjects. However, data from the Department for Environment, Food and Rural Affairs study (DEFRA, 2011) suggests that energy intake from food and drink in the UK population has been declining since the 1980 (Figure 2).
Figure 2. Trends in average energy intake from food and drink in 2009 (Source: Family Food in 2009, DEFRA
This is paradoxical, given that this is the period that has seen the most rapid increase in the prevalence of obesity. However, it has been shown that the type of food has changed. The consumption of cheap fast food and energy-dense food high in fat and/or sugar has increased (Stubbs et al., 1995), whilst more expensive healthy food such as fruit and vegetables has declined. Therefore it is the obligation of policy makers and businesses to ensure that healthy foods are readily available and promoted at affordable prices. This is an essential long term and large-scale commitment to reverse the obesity epidemic.
In conclusion, it appears that the coupling between energy intake and energy expenditure is at the heart of the obesity epidemic, both of which are greatly influenced by psychosocial factors and the environment in which we live and work. Currently the evidence points to changes in the level of physical activity and food system, which is producing more processed, affordable, and effectively marketed high-energy food. These changes in my opinion have lead to a positive energy balance causing the obesity epidemic. Policies that encourage and promote physical activities and a change towards healthier food are needed to reverse the epidemic.
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